Among the earliest semi-synthetic cephalosporins discovered were the so-called cephalosporin C.sub.A (pyridine) type compounds which have a pyridinium or substituted pyridinium group at the 3' position of the cephem ring structure. The first pyridinium substituted cephalosporin was discovered by E. P. Abraham shortly after his discovery of cephalosporin C itself. See E. P. Abraham, et al., U.S. Pat. No. 3,226,384. The first and only cephalosporin C.sub.A derivative to find clinical use was cephalosporine, E. H. Flynn, U.S. Pat. No. 3,449,338. Spencer reviewed the earlier cephalosporin C.sub.A type compounds, J. L. Spencer, et al., "Chemistry of Cephalosporin Antibiotics VIII. Synthesis and Structure-Activity Relationships of Cephaloridine Analogues," Antimicrobial Agents and Chemotherapy-1966, pp. 573-580.
Recently, Heymes, et al., U.S. Pat. No. 4,152,432 describe cephalosporin antibiotics having a 7-(2-aminothiazol-4-yl)-2-oximinoacetamido side chain with the traditional acetoxymethyl group in the 3-position. These compounds are reported to be potent parenteral antibiotics. More recently C.sub.A (pyridine) compounds have been prepared which have the same 2-aminothiazole oxime substituted side chain. O'Callaghan, et al., U.K. patent application No. 2,025,398A describe such compounds having the pyridinium or a 3- or 4-carbamoylpyridinium group in the 3-position, while the oxygen atom of the .alpha.-oximino group is substituted with a --C(CH.sub.3).sub.2 COOH group. Belgium Patent Specification No. 853,545 teaches certain 2-aminothiazole methoxyimino compounds substituted in the 3-position by pyridinium and substituted pyridinium.